1) Field of the Invention
The present invention relates to an optical module produced by assembling a plurality of optical waveguide parts (for example, optical wave transmitting parts) used, for example, for optical communication and a mounting deviation compensation method for an optical waveguide part.
2) Description of the Related Art
In recent years, attention is paid to a mounting technique (optical integration technique) for hybrid integrating optical parts on an Si platform or a PLC (Planar Lightwave Circuit) platform as a technique suitable for satisfaction of a demand for mass production and reduction in cost of an optical module.
Further, a mounting technique (planar mounting technique) which uses a PLC platform as a mounting substrate is considered suitable for downsizing of an optical module and simplification of an assembly process because optical parts are carried on a common substrate on the surface of which a waveguide is formed.
Where an optical part (optical waveguide device) is mounted on a platform (optical waveguide substrate), it is common to perform an aligning operation using an active alignment technique for adjusting the position of an optical part while monitoring the actual optical coupling efficiency.
Further, where an optical device (optical waveguide device) is of a type wherein a light beam propagates along the surface of the device and goes out from an end face of the device or of another type wherein a light beam incoming from an end face of the device propagates along the surface of the device and goes out from another end face of the device such as, for example, an optical modulator formed using lithium niobate (LN), a Fabry-Perot type semiconductor laser or the like is commonly coupled to a linearly disposed optical fiber or optical waveguide through a lens provided in the proximity of the end face of the device.
It is to be noted that, through a prior art search conducted, Japanese Patent Laid-Open No. 2002-23205, Japanese Patent Laid-Open No. Hei 3-256030, and David W. Vernooy, “Alignment-Insensitive Coupling for PLC-Based Surface Mount Photonics”, IEEE PHOTONICS TECHNOLOGY LETTERS, Vol. 16, No. 1, pp.269-271, JANUARY 2004 (hereinafter referred to as David) were found.
Japanese Patent Laid-Open No. 2002-23205 discloses an optical device wherein a voltage is applied to a cladding layer formed between two optical waveguides in a semiconductor optical waveguide to vary the refractive index of the cladding layer to vary the coupling length so that a wavelength of light to be extracted can be selected (for example, refer to the second embodiment).
However, in the optical device disclosed in Japanese Patent Laid-Open No. 2002-23205, only the coupling length between the optical waveguides disposed in accuracy and formed integrally by a semiconductor process is varied so that the wavelength of light to be extracted can be selected, but a plurality of optical waveguide parts are not involved. Particularly, in the optical device disclosed in Japanese Patent Laid-Open No. 2002-23205, such a subject as of the present invention that “the variation of the physical distance between waveguide cores which appears upon assembling can be compensated for and a sufficient optical coupling efficiency can be obtained” is not supposed at all.
Japanese Patent Laid-Open No. Hei 3-256030 discloses an optical device wherein, where an outgoing angle (emitting angle) is varied by a temperature variation or the like, an electric field is applied to an optical waveguide having an electro-optic effect to vary the refractive index so that the optical axis of outgoing light (emitting light) can be maintained fixedly (refer to, for example, descriptions in “Subject to Be Solved by the Invention”, “Means for Solving the Subject” and “Operation” of the specification).
However, Japanese Patent Laid-Open No. Hei 3-256030 only discloses the optical device wherein an electric field is applied to an optical waveguide having an electro-optic effect to vary the refractive index of the optical waveguide so that the optical axis of outgoing light can be maintained fixedly, but does not disclose provision of a plurality of optical waveguide parts. Particularly, such a subject as of the present invention that “the variation of the physical distance between waveguide cores which appears upon assembling can be compensated for and a sufficient optical coupling efficiency can be obtained” is not supposed at all.
David discloses a method wherein, where an optical waveguide device is mounted on an optical waveguide substrate, individual optical waveguides of the optical waveguide device and the optical waveguide substrate are disposed closely and in parallel to each other so that evanescent components of optical waves are coupled to each other.